Blender freezes when rendering,building the last samples
For laptop users:

On any render, my computer (the whole screen) would freeze about 5 seconds, and after some seconds it would freeze again.

To fix, I had to go to File -> User Preferences -> System and on the bottom-left side I picked CUDA for the "Cycles Compute Device", and this fixed the problem.





It seems very noob-ish because it actually is! And it worked for me since I am a beginner, I hope this helps another beginner searching this on Google.